Over 30% of pregnant women in the United States are obese. This high prevalence of obesity is, in large part, due to lifelong consumption of an obesity promoting energy dense diet that gets most of its calories from fat and simple sugars - the so called Western Diet. There is a growing body of evidence that Western diet consumption by pregnant women can cause negative changes in the placenta's metabolism - the processes by which the placenta breaks down nutrients to obtain energy. The placenta is a specialized organ that acts as the life support system for unborn babies developing in their mother's uterus. Impaired function of placental metabolism is one of the most common problems affecting pregnancy. These changes in placental metabolism are suspected to cause changes in the baby's metabolism that lead to increased risks for developing obesity and related diseases like heart disease and diabetes later in life. Unfortunately, current methods for assessing the metabolic function of the placenta during pregnancy provide only indirect measures, greatly limiting their utility. This means that we have a very limited understanding of how obesity and Western Diet consumption affect placental metabolism. There is a critical need for direct measurement of metabolic changes in the placenta. We are proposing to develop a new technology based on Magnetic Resonance Imaging (MRI) that will, for the first time, allow direct measurement of metabolic processes in the placenta during pregnancy. We can inject a modified version of substances used for energy production in the placenta so that they become visible on images produced by a specially modified MRI system. These images will allow us to see metabolism in the placenta and monitor changes in placental function. In this proposal, we will perform experiments in an animal model of human pregnancy and in pregnant women to demonstrate that this technology can be used without compromising the health of the mother and unborn baby. We will then demonstrate the ability of this technique to detect differences in placental metabolism between normal pregnancies and abnormal pregnancies that are caused by the mother's lifelong consumption of the Western Diet. At the successful completion of our project, we will have demonstrated a safe method for measuring placental metabolism that will open a new window into the investigation of the effect of exposing the placenta to lifelong consumption of the Western Diet.